Mechanically Controlled Landslide Deformation

Many landslide models assume a fully deformable body without any resistance against deformation. However, in reality, landslide bodies can display negligible to large deformation during motion. Examples for limited deformation include the prehistoric giant landslides of Flims and Köfels, or the Vajont landslide of 1963, where the structure of rock largely remained intact and the slides did not evolve into rock avalanches. Here, we propose a novel mechanical model for the controlled deformation of landslides. The model is based on the principle of material strength or resistance and includes a user-specified function that reflects the mechanisms (internal friction, cohesion, viscosity, and yield strength) that act against the deformation induced by the free-surface or the hydraulic pressure gradient of the landslide. This controls the landslide deformation and, in turn, also the motion and run-out, and offers a unique possibility to describe the landslide motion ranging from a fully non-deformable body sliding along the mountain slope to a completely fluidized motion without any resistance against the force associated with the free-surface pressure gradient. The latter is the situation often considered for the motion of granular flows such as avalanches of snow or rock, or debris flows. The former can play a substantial role in the dynamics, however, has not yet been considered in mass flow simulations, severely limiting the applicability of those models. We demonstrate the performance of the new model and its applicability, also with the advanced open-source computational mass flow simulation tool r.avaflow.